Here's what I made for Otakon 2009: Alex Mercer from the game [Prototype]. Ironically I haven't played the game yet, so I thought if I can't play the game I might as well cosplay the main character.
The Blade Arm is comprised of cardboard, masking tape, and tin foil. It took a long ass time to finish: maybe about a week straight if I put all the times together.
Mercer's jacket was a bitch to complete as well. When I bought it, it was originally silver, so I had to spray paint it black. Unfortunately, the jacket started sticking to itself because of the paint, therefore a lot of the black peeled off, revealing the silver and whatever was under the original paint coat. I ended up not fixing those areas and leaving it the way it was; it kinda gave off the "really worn out" look, which was pretty sweet considering the style and setting of [Prototype]. I also made the white stripes and red design on the jacket as well.
In conclusion, this is probably my first cosplay in which I practically made everything, not just the prop. It was a pain in the neck and took a lot of time and patience, but I think it really paid off in the end.
I'll try to post some pics of the actual cosplay when I can.